1. Field of the Invention
The subject matter of the invention includes a process for recovery of pure acetone from the crude acetone containing aldehydic impurities and unreacted cumene which is obtained from the cleavage of cumene hydroperoxide.
2. Description of Related Art
An important process for production of phenol and acetone is the cumene hydroperoxide process wherein benzene is alkylated to cumene, which is oxidized to cumene hydroperoxide, which, in turn, is cleaved to produce phenol and acetone.
Varying amounts of side products such as aldehydes, particularly acetaldehyde and propionaldehyde, and other materials such as mesityl oxide, dimethylphenylcarbinol, alphamethylstyrene and acetophenone also result.
Phenol can be recovered by fractional distillation, with a crude acetone fraction removed from overhead. The crude acetone fraction contains those side products discussed above, as well as hydrocarbons such as unreacted cumene and alphamethylstyrene and traces of organic acids such as formic acid.
U.S. Pat. No. 4,430,447 to Laverick et al. describes a process for recovery of pure acetone from a crude acetone fraction which requires partial condensation of the crude acetone fraction, then feeding the resulting vapor phase only to a second distillation column for treatment with an alkaline material and distillation.
U.S. Pat. No. 3,668,256 to Brundege describes a process of fractionally distilling crude acetone in a single, multiplate column while continuously adding to the column aqueous alkali metal hydroxide at a specified ratio to reflux rate, in an amount and concentration sufficient to polymerize aldehyde impurities. Caustic strength is controlled by the ratio of reflux to caustic feed.
In practice, problems are encountered with the Brundege process if the crude acetone feed stream contains appreciable amounts of hydrocarbons, particularly unreacted cumene, which are not first removed from the crude acetone feed. It is desirable from a process and economic viewpoint to introduce substantially the entire crude acetone fraction, vapor and liquid, including any hydrocarbons and side-products that may be present. However, the cumene present in the crude acetone creates a cumene-rich oil phase which causes problems in operation of the column. The presence of an oil phase creates difficulty in caustic/aldehyde contact since the aldehydes are soluble in the oil phase and the caustic must then diffuse into the oil phase for contact. In practicing the Brundege process, the oil phase must be drawn off as a sidedraw from a plate or plates below the point of crude acetone feed. The inevitable result of the sidedraw of the oil phase is that economically significant amounts of the liquid phase containing caustic and acetone is drawn off also which must be separated from the oil and recycled with the caustic feed. This, however, creates further problems by introducing aldol condensation products, for example diacetone alcohol and further degradation products such as mesityl oxide, into the caustic feed, which can contact the acetone and increase the chance of acetone quality upsets.
The need exists for an efficient, economical process for the recovery of acetone from cumene-containing crude acetone.